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Subject: Re: [office] chart:interpolation
Andreas,OK, I will defer edits on this issue pending your proposal and any action by the TC.
Thanks! Hope you are having a great day! Patrick On 11/08/2011 04:16 PM, Andreas J. Guelzow wrote:
On Mon, 2011-11-07 at 13:36 -0700, Patrick Durusau wrote:Andreas, On 11/03/2011 04:36 PM, Andreas J. Guelzow wrote: <snip>I wasn't as confused as I thought.That's always a comfort. ;-)A small bug in the current development version of Gnumeric hid some of the interpolation methods implemented there. So I will be proposing a few more methods: * Cubic spline interpolation with parabolic limits. * Cubic spline interpolation with cubic limits. * Cubic spline interpolation with fixed derivatives at both ends. Rather than adding more attribute values to the chart:interpolation attribute, I believe it would be cleaner (and more in the spirit of the already existing chart:spline-* attribute) to use secondary attributes chart:spline-limits, chart:spline-limits-start, chart:spline-limits-end that would modify the cubic-spline interpolation already provided in ODF 1.2.To confirm before you enter them in JIRA: chart:spline-limits chart:spline-limits-start chart:spline-limits-end Valuetype = ?Until the proposal is finished, I don't think I am sure which value types will be the most appropriate. chart:spline-limits-start/end are probably going to be expressions that shall evaluate to a number. chart-spline-limits will be some kind of enumeration.What do we have to reference in current 20:26? (I know it is probably obvious but we should not simply say: apply to 20:26 as appropriate.)In 20.26 this would not affect the text for the step functions but it will change the limit handling in the cubic splines.On prose for these attributes, let's avoid:20.51 If the chart:spline-resolution attribute has value 1 this is identical to the chart:interpolation attribute value none.That is really awkward and I am not altogether sure it is necessary.I am not sure why that sentence is preceded by "20.51" (that's the section describing "chart:spline-resolution".) The purpose of that sentence is intended to provide a definition for b-spline (and cubic-spline) in the case of the resolution 1. Of course one could omit that sentence since in the case resolution == 1 the described method yields the same result as using method none.Unless we mean to bind the value of chart:spline-resolution to chart:interpolation? That is if chart:spline-resolution> 1 then chart:interpolation *cannot* have the value of none?Gnumeric also provides: * Closed Bezier cubic spline interpolation. Since this is not really a proper "interpolation" method, I am not sure this would be appropriately added here unless other implementations provided a similarly closed interpolation.Other implementers? Anyone?My comment wasn't quite correct. The description of the cubic-spline method reflects the implementation in LibreOffice/OpenOffice: If the first and last data point are the same then a closed cubic spline is created otherwise an open one. In Gnumeric one would need to specify whether one wants a closed or open cubic spline, there is no automatic guessing of whether a closed or open spline is used. (Note that an "open" spline with the first and last data point the same simply has a corner at that point. This is something that may be expected by a user and provides a continuous behaviour as the last and first data point approach each other.) So I will make a proposal that allows both behaviours to be specified. Andreas
-- Patrick Durusau firstname.lastname@example.org Chair, V1 - US TAG to JTC 1/SC 34 Convener, JTC 1/SC 34/WG 3 (Topic Maps) Editor, OpenDocument Format TC (OASIS), Project Editor ISO/IEC 26300 Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps) Another Word For It (blog): http://tm.durusau.net Homepage: http://www.durusau.net Twitter: patrickDurusau